dm: core: Prepare for updating the device tree with ofnode
Add some documentation and a new flag so that we can safely enabled using
the ofnode interface to write to the device tree.
Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/doc/develop/driver-model/livetree.rst b/doc/develop/driver-model/livetree.rst
index c29f29b..faf3eb5 100644
--- a/doc/develop/driver-model/livetree.rst
+++ b/doc/develop/driver-model/livetree.rst
@@ -224,6 +224,32 @@
freed. Then the tree can be scanned for these 'separately allocated' nodes and
properties before freeing the memory block.
+The ofnode_write\_...() functions also support writing to the flat tree. Care
+should be taken however, since this can change the position of node names and
+properties in the flat tree, thus affecting the live tree. Generally this does
+not matter, since when we fire up the live tree we don't ever use the flat tree
+again. But in the case of tests, this can cause a problem.
+
+The sandbox tests typically run with OF_LIVE enabled but with the actual live
+tree either present or absent. This is to make sure that the flat tree functions
+work correctly even with OF_LIVE is enabled. But if a test modifies the flat
+device tree, then the live tree can become invalid. Any live tree tests that run
+after that point will use a corrupted tree, e.g. with an incorrect property name
+or worse. To deal with this we use a flag UT_TESTF_LIVE_OR_FLAT then ensures
+that tests which write to the flat tree are not run if OF_LIVE is enabled. Only
+the live tree version of the test is run, when OF_LIVE is enabled, with
+sandbox_flattree running the flat tree version.
+
+This is of course a work-around, even if a reasonable one. One solution to this
+problem would be to make a copy of the flat tree before the test and restore it
+afterwards, in the same memory location, so that the live tree pointers work
+again. Another would be to regenerate the live tree if a test modified the flat
+tree.
+
+Neither of these solutions is currently implemented, since the situation that
+causes the problem can only occur in sandbox tests, is somewhat esoteric and
+the UT_TESTF_LIVE_OR_FLAT flag deals with it in a reasonable way.
+
Multiple livetrees
------------------
diff --git a/include/test/test.h b/include/test/test.h
index 0104e18..c888d68 100644
--- a/include/test/test.h
+++ b/include/test/test.h
@@ -46,6 +46,8 @@
UT_TESTF_CONSOLE_REC = BIT(5), /* needs console recording */
/* do extra driver model init and uninit */
UT_TESTF_DM = BIT(6),
+ /* live or flat device tree, but not both in the same executable */
+ UT_TESTF_LIVE_OR_FLAT = BIT(4),
};
/**
diff --git a/test/test-main.c b/test/test-main.c
index ee38d1f..c0d0378 100644
--- a/test/test-main.c
+++ b/test/test-main.c
@@ -338,7 +338,8 @@
/* Run with the live tree if possible */
runs = 0;
if (CONFIG_IS_ENABLED(OF_LIVE)) {
- if (!(test->flags & UT_TESTF_FLAT_TREE)) {
+ if (!(test->flags &
+ (UT_TESTF_FLAT_TREE | UT_TESTF_LIVE_OR_FLAT))) {
uts->of_live = true;
ut_assertok(ut_run_test(uts, test, test->name));
runs++;